mail using a C program

linuxprogrammer · 07-19-2004, 01:22 PM

In a C program of mine, I want to mail a message to root if certain conditions are met. How do I send the mail? If there is some mailing library, it'll be very helpful to have its name and description.

jim mcnamara · 07-19-2004, 01:43 PM

Here is one way:

Code:

char fpBuffer[128]={'\0'};
.........
sprintf (fpBuffer,
          "/usr/bin/mailx -s '%s' %s < %s",
          "Email Report",
          EmailId,
          RptName);
       system (fpBuffer);

linuxprogrammer · 07-20-2004, 08:52 AM

Quote:

Originally posted by jim mcnamara
Here is one way:

Code:

char fpBuffer[128]={'\0'}; ......... sprintf (fpBuffer, "/usr/bin/mailx -s '%s' %s < %s", "Email Report", EmailId, RptName); system (fpBuffer);

Thanks.

I tried this on two machines of mines.

This works on one, where I use Linux directly from my Knoppix CD. But even when I tried sending mail directly from the prompt, it took about 10-15 minutes for root to receive the message. What may be the cause of this delay?

Another machine of mine, when I attempted to send a mail from the command prompt said there was some problem with the name server. This machine is on LAN. How can I correct the problem?

afm · 07-20-2004, 11:31 PM

Please, don't use the sample code above.

It has severe security flaws, like allowing for buffers overflows and shell escape sequences attacks.

To send mail using C, try this (untested) code snippet:

Code:

#define SENDMAIL "/usr/sbin/sendmail -i -t"
FILE *sm;
sm = popen(SENDMAIL, "w");
if ( !sm )
{
   your_errno_handling_routine();
   return 1;
}

fprintf(sm, "From: %s\n", from);
fprintf(sm, "To: %s\n", to);
fprintf(sm, "Subject: %s\n", subject);
/* print other headers here */
fputc('\n', sm);
fputs(message, sm);

if ( pclose(sm) == -1 )
{
   your_errno_handling_routine();
   return 1;
}

The trickiest part is to find the correct value for the SENDMAIL macro constant. There's is no standard command line to run the system mailer, though calling /usr/sbin/sendmail and a subset of its parameters is becoming a de facto standard (even other mailers, such as Postfix, install a somewhat compatible /usr/sbin/sendmail).

If you want to write portable programs, use autoconf to discover a sane value for SENDMAIL.

foo_bar_foo · 07-20-2004, 11:56 PM

since you are writing in c you could always just implement smtp and talk to the server on "localhost"
too long code to start posting but you can find examples..
I like this solution better than piping

Tinkster · 07-21-2004, 12:08 AM

Moved: This thread is more suitable in Programming and has been moved accordingly to help your thread/question get the exposure it deserves.

Cheers,
Tink